Film readers for projecting an image onto a screen in which the image is contained on a microfiche are well known in the art. With respect to film readers used in conjunction with microfiche transparencies, the transparency is normally mounted on a carrier slidably movable relative to the optical axis of a lens to position a selected image frame in relation to the optical axis. Generally, the microfiche is placed between glass plates to maintain the microfiche in a flat plane throughout its movement to locate a selected image frame. Such apparatus is fairly complex and does not lend itself to the construction of a compact, portable low cost microfiche reader.
Other forms of so called portable microfiche readers are shown in U.S. Pat. Nos. 3,718,390 and 3,851,960. While the devices disclosed in these patents are portable in the sense that they may be carried from one location to another, because they include projection and display means which add to the cost and bulkiness of the devices, they are not inexpensive, compact readers of the kind adapted to be hand-held during operation as in the present invention.
Still another microfiche viewer is shown in U.S. Pat. No. 4,149,776. While this device is portable and adapted to be hand-held during operation, it does not provide means for readily selecting a desired image frame of the microfiche to be viewed. Thus, the device comprises a slide tube having a window near one of its ends which acts as a film gate, a mirror positioned in line with the window, a magnification and an eyepiece lens and a transparent tube for supporting a microfiche mounted within a diffuser tube.
To view a desired image frame, it is necessary to rotate the slide tube until the window lines up with a selected column of the microfiche, and then move the slide tube axially until the image frame of a selected row of the microfiche is in line with the window. The image is then viewed through the slide tube which forms anoptical path. Such an arrangement results in a trial and error method of locating the desired image frame to be viewed and, additionally, requires accurate alignment of the window with the image frame in order to reflect the image from the mirror to the optical path.